The invention relates generally to heating, ventilating, and air conditioning systems (HVAC), and more particularly to HVAC systems employing hot gas reheat for humidity control.
A wide range of applications exists for HVAC systems. For example, residential, light commercial, commercial, and industrial systems are used to control temperatures and air quality in residences and buildings. Very generally, HVAC systems may include circulating a fluid, such as a refrigerant, through a closed loop between an evaporator where the fluid absorbs heat and a condenser where the fluid releases heat. The fluid flowing within the closed loop is generally formulated to undergo phase changes within the normal operating temperatures and pressures of the system so that considerable quantities of heat can be exchanged by virtue of the latent heat of vaporization of the fluid.
HVAC units, such as air handlers, heat pumps, and air conditioning units, are used to provide heated, cooled, and/or dehumidified air to conditioned environments. Dehumidification may be desired on days when the temperature is cool and there is a high humidity level, such as damp, rainy, spring and fall days. Further, certain spaces, such as refrigerator cases, locker rooms, food production lines, art galleries, and museums, may benefit from a low humidity environment. Accordingly, it may be desirable to operate an HVAC system in a reheat dehumidification mode.
In the reheat mode, humidity may be removed by cooling and then reheating air that is provided to the conditioned space. The air can be reheated using electric or gas heat; however, these heating methods may be costly. The air also can be reheated by passing the air over a reheat heat exchanger that circulates heated refrigerant from the closed loop of the HVAC system. However, when the refrigerant is circulated through the reheat heat exchanger, it may be difficult to maintain a consistent refrigerant charge level within the HVAC system. Further, additional equipment, such as a second compressor, may be desired when employing a reheat heat exchanger within a HVAC system.